Have You Seen This Disease?  

Cranberry Stem Gall, aka "Canker"

Symptoms from the dike appear as patches of unthrifty or dead uprights. Runners and/or uprights are swollen with bumps and galls erupting through the bark. The current year’s growth is stunted or dead. Symptoms have been noticed in early July, but extensive damage is usually not detected until late July through September. When galls first emerge, they are soft, green, and moist. Later they shrink and become hard and brown to black. If the galls become large and encircle the stem, they apparently crush the vascular cambium thereby killing tissues above the galled area. Within a few weeks, an upright can go from looking healthy with large fruit starting to color, to completely withered with brown leaves and dried-up fruit. Stem tissue below the galled area is green and often sends out new shoots.

What causes stem gall? This is the subject of ongoing research. The cause of stem gall is probably two species of soil-borne bacteria that infect plants through wounds.

How is stem gall managed? It is impossible to eliminate the pathogen with pesticides. Because the bacteria probably infect through wounds, avoid physical injury to plants. This would include damage during harvest, root-feeding insects, and freezing/thawing during fall through spring. Do not propagate cuttings from a diseased bed.